US6119523A - Method and apparatus for electronic compensation of erroneous readings caused by resonance in a capacitive pressure transducer - Google Patents

Method and apparatus for electronic compensation of erroneous readings caused by resonance in a capacitive pressure transducer Download PDF

Info

Publication number
US6119523A
US6119523A US09/308,409 US30840999A US6119523A US 6119523 A US6119523 A US 6119523A US 30840999 A US30840999 A US 30840999A US 6119523 A US6119523 A US 6119523A
Authority
US
United States
Prior art keywords
transducer
resonance
pressure transducer
capacitive pressure
compensation
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US09/308,409
Other languages
English (en)
Inventor
Ray Olsson
Per Bjorkman
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Inficon Aaland AB
Original Assignee
Balzers and Leybold Instrumentation AB
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Balzers and Leybold Instrumentation AB filed Critical Balzers and Leybold Instrumentation AB
Assigned to BALZERS AND LEYBOLD INSTRUMENTATION AB reassignment BALZERS AND LEYBOLD INSTRUMENTATION AB ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BJORKMAN, PER, OLSSON, RAY
Application granted granted Critical
Publication of US6119523A publication Critical patent/US6119523A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L9/00—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means
    • G01L9/12—Measuring steady of quasi-steady pressure of fluid or fluent solid material by electric or magnetic pressure-sensitive elements; Transmitting or indicating the displacement of mechanical pressure-sensitive elements, used to measure the steady or quasi-steady pressure of a fluid or fluent solid material, by electric or magnetic means by making use of variations in capacitance, i.e. electric circuits therefor

Definitions

  • the present invention concerns a method for measuring pressure using a capacitive pressure transducer and a pressure measuring device comprising a capacitive pressure transducer according to the preamble of claim 10.
  • Capacitive pressure transducers are known from JP-A-04 104 027 and EP-A-0 194 953. The latter may also be used for measuring force or acceleration. Its properties are determined and resonance avoided during use.
  • the purpose of the present invention is to remove the drawbacks of the prior art and to provide a method and device for measuring pressure where the influence of resonance in the capacitive pressure transducer is compensated.
  • the invention is based on the concept of causing the capacitive pressure transducer to resonate, measuring the erroneous reading caused by the resonance and feeding a feedback compensation signal to the measuring element where the signal is essentially unfiltered.
  • the device according to the invention is based on the concept of an apparatus for compensating effects of resonance comprising error detection and compensation elements whose upper barrier frequency is above the resonance frequency of the transducer, for detecting an erroneous reading of the transducer and for generating a compensation signal to be fed into the detection elements.
  • the invention provides considerable benefits.
  • the compensation is most efficient and, in the case of undistorted self-oscillation, it will eliminate the erroneous reading to 100%.
  • FIG. 1 is a side view of the basic scheme of a capacitive pressure transducer that can be used in the invention
  • FIG. 2 depicts a typical known measuring circuit for the pressure transducer of FIG. 1;
  • FIG. 3 is a more detailed illustration of element F1 in FIG. 2;
  • FIG. 4 depicts a coupling according to the invention for electronic compensation of erroneous readings caused by resonance in a capacitive pressure transducer.
  • the type of pressure transducers described herein are generally called capacitance manometers.
  • the pressure to be measured acts on one side of the membrane, whereas its other side is under a reference pressure which is usually very low.
  • a capacitance manometer When pressure is measured exploiting the movements of the membrane even a number of parasitic parameters are generated which in no way contribute positively to the measurement.
  • One of these parameters comprises the natural resonance frequency of the membrane. At this frequency the membrane self-oscillates with a minimum of external energy input. Based on mere intuition, it is obvious that such self-oscillation of the membrane will interfere with the measurement. On the basis of practical measurements it is also known that this is the case.
  • FIG. 1 depicts the transducer element with membranes and current measuring electrodes.
  • an electrode 4 has been arranged on its inner side in the reference vacuum space 3 and a second electrode 5 on the housing body 7 in the same space. Connecting wires 6 lead from these electrodes 4 and 5 to the outer side of the transducer housing.
  • the membrane 2 is fixedly tensioned between the transducer housing 7 and the bottom part 8 by means of glass joints 9 and moves in toward the level of the transducer housing 7 under elevated pressure.
  • the capacitance is inversely proportional to the distance of the electrodes and therefore also to the pressure.
  • Cp is the capacitance between the electrodes 4 and 5 of the transducer element 1 in the capacitor according to FIG. 2 and thus, it represents the distance between these, said distance in turn being proportional to the pressure.
  • a parallelogram signal having a frequency of 8 kHz (Q) feeds the two switches SW1 and SW2.
  • Uk is a reference voltage which in reality is a parallelogram signal having the same frequency as Q and having a constant amplitude.
  • the output signal is proportional to the reference voltage Uk ##EQU8## and the reference capacitance Cr and inversely proportional to the measured capacitance.
  • the output signal is proportional to the distance between the electrodes wherefore it is also proportional to the pressure.
  • the membrane is shifted in relation to the pressure, whereby the distance between the electrodes is altered resulting in altered capacitance.
  • the oscillation is damped and occurs at the resonance frequency of the membrane. If force is instead introduced in the form of pulses or waves in the material having the same frequency as the resonance frequency of the membrane, the self-oscillation is increased and then maintained constant at a certain amplitude where the introduced energy and energy losses are the same. In connection with this type of membrane movement (resonance) the amplitude can become great and even exceed the entire normal measurement range. In spite of this circumstance the membrane still measures the static pressure of the gas in front of the membrane. However, a positive deviation is now added to the measurement result, the deviation being proportional to the quadrature of the amplitude of the self-oscillation.
  • Us will not be equal to Uk at the resonance frequency but will instead vary proportional to the capacitance.
  • the relation is the same as in the previous case.
  • Us can be separated by measuring the difference between Us and Uk by means of a circuit whose barrier frequency is clearly beyond the resonance frequency.
  • Us is a sinusoidal voltage with the resonance frequency of the membrane. This alternating voltage is amplified, rectified, filtered and scaled for returning to the summing point between R2 and R3.
  • FIG. 4 shows the circuit in practice.
  • the signal Us is compared to Uk between the resistances R4 and R5 and is then amplified.
  • the signal is rectified by the diode D and is filtered by the low-pass filter F4, and at the output phase offset is adjusted by F5, whereafter the output voltage Ures is fed back to the nodal point between R2 and R3 via a resistor R res .
  • the compensation takes place such that the membrane is caused to resonate by means of a variable tone generator.
  • the erroneous reading of the output signal is recorded during resonance as compared to non-resonance.
  • the signal Ures from the compensation circuit is switched and scaled until no difference between Uut during resonance and non-resonance is measurable.
  • the compensation is very efficient and, in the case of undistorted self-resonance, able to eliminate the erroneous reading to 100%. This can be done during calibration of the transducer.
  • Resonance problems of this type can occur in certain systems due to unsuccessful coaction of vibrations from pumps and the system design.
  • the compensation circuit is in such case a must if measurements are to be performed. Often the resonance in such cases tends to be variable in time and size, wherefore the output signal without compensation varies in the second power in view of these error sources in a most disturbing ripple.
  • the measurement signal can be rectified by quadration.
  • a rectifier can even be used which generates a voltage that is a function of the amplitude of the membrane oscillation.
  • the measurement error can also be made modulation dependent in the desired manner by varying the amplification prior to the rectifier and by varying the degree of modulation where the error is zero.

Landscapes

  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Fluid Pressure (AREA)
  • Control Of Motors That Do Not Use Commutators (AREA)
  • Measurement Of Resistance Or Impedance (AREA)
  • Filters And Equalizers (AREA)
US09/308,409 1996-12-13 1997-12-12 Method and apparatus for electronic compensation of erroneous readings caused by resonance in a capacitive pressure transducer Expired - Lifetime US6119523A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FI965016 1996-12-13
FI965016A FI101018B (sv) 1996-12-13 1996-12-13 Förfarande och anordning för elektronisk kompensation av missvisning t ill följd av resonans hos en kapacitiv tryckgivare
PCT/IB1997/001562 WO1998026262A1 (en) 1996-12-13 1997-12-12 Method and apparatus for electronic compensation of erroneous readings caused by resonance in a capacitive pressure transducer

Publications (1)

Publication Number Publication Date
US6119523A true US6119523A (en) 2000-09-19

Family

ID=8547270

Family Applications (1)

Application Number Title Priority Date Filing Date
US09/308,409 Expired - Lifetime US6119523A (en) 1996-12-13 1997-12-12 Method and apparatus for electronic compensation of erroneous readings caused by resonance in a capacitive pressure transducer

Country Status (7)

Country Link
US (1) US6119523A (de)
EP (1) EP0944817B1 (de)
JP (1) JP2001506006A (de)
AT (1) ATE213541T1 (de)
DE (1) DE69710606T2 (de)
FI (1) FI101018B (de)
WO (1) WO1998026262A1 (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7161476B2 (en) 2000-07-26 2007-01-09 Bridgestone Firestone North American Tire, Llc Electronic tire management system
US20080184804A1 (en) * 2004-12-27 2008-08-07 Thales Resonator Measurement Device and Method Employing the Device
US20110056302A1 (en) * 2008-04-23 2011-03-10 Nxp B.V. Electronic circuit for controlling a capacitive pressure sensor and capacitive pressure sensor system
US20110215188A1 (en) * 2010-03-04 2011-09-08 Dispensing Dynamics International Paper towel dispensing systems
US8266465B2 (en) 2000-07-26 2012-09-11 Bridgestone Americas Tire Operation, LLC System for conserving battery life in a battery operated device
US20140260647A1 (en) * 2013-03-13 2014-09-18 Invensense, Inc. Pressure sensor stabilization

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6837112B2 (en) * 2003-03-22 2005-01-04 Stec Inc. Capacitance manometer having a relatively thick flush diaphragm under tension to provide low hysteresis
US7554343B2 (en) 2005-07-25 2009-06-30 Piezoinnovations Ultrasonic transducer control method and system
KR101355098B1 (ko) 2012-10-10 2014-02-04 주식회사 오토산업 용량성 압력센서의 출력제어회로
JP6357090B2 (ja) * 2014-12-02 2018-07-11 株式会社堀場エステック 静電容量型センサ

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2578323B1 (fr) * 1985-03-01 1987-11-20 Metravib Sa Capteur integre de grandeurs mecaniques a effet capacitif et procede de fabrication.
JP2905902B2 (ja) * 1990-08-24 1999-06-14 横河電機株式会社 半導体圧力計およびその製造方法

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
Puers B et al. "a capacitive pressure sensor with low impedance output and active suppression of parasitic effects", sensors and actuators, vol. A21, No. 1/03, Feb. 1, 1990, pp. 108-114, XP000149570.
Puers B et al. a capacitive pressure sensor with low impedance output and active suppression of parasitic effects , sensors and actuators, vol. A21, No. 1/03, Feb. 1, 1990, pp. 108 114, XP000149570. *

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7161476B2 (en) 2000-07-26 2007-01-09 Bridgestone Firestone North American Tire, Llc Electronic tire management system
US8151127B2 (en) 2000-07-26 2012-04-03 Bridgestone Americas Tire Operations, Llc System for conserving battery life in a battery operated device
US8266465B2 (en) 2000-07-26 2012-09-11 Bridgestone Americas Tire Operation, LLC System for conserving battery life in a battery operated device
US20080184804A1 (en) * 2004-12-27 2008-08-07 Thales Resonator Measurement Device and Method Employing the Device
US7798005B2 (en) * 2004-12-27 2010-09-21 Thales Resonator measurement device and method employing the device
US20110056302A1 (en) * 2008-04-23 2011-03-10 Nxp B.V. Electronic circuit for controlling a capacitive pressure sensor and capacitive pressure sensor system
US8516894B2 (en) * 2008-04-23 2013-08-27 Nxp B.V. Electronic circuit for controlling a capacitive pressure sensor and capacitive pressure sensor system
US20110215188A1 (en) * 2010-03-04 2011-09-08 Dispensing Dynamics International Paper towel dispensing systems
US8511599B2 (en) 2010-03-04 2013-08-20 Richard LaLau Paper towel dispensing systems
US20140260647A1 (en) * 2013-03-13 2014-09-18 Invensense, Inc. Pressure sensor stabilization
US9880063B2 (en) * 2013-03-13 2018-01-30 Invensense, Inc. Pressure sensor stabilization

Also Published As

Publication number Publication date
WO1998026262A1 (en) 1998-06-18
EP0944817B1 (de) 2002-02-20
DE69710606T2 (de) 2002-11-21
ATE213541T1 (de) 2002-03-15
JP2001506006A (ja) 2001-05-08
EP0944817A1 (de) 1999-09-29
DE69710606D1 (de) 2002-03-28
FI101018B (sv) 1998-03-31
FI965016A0 (fi) 1996-12-13

Similar Documents

Publication Publication Date Title
TW434402B (en) Capacitive pressure sensing method and apparatus
EP0136248B1 (de) Ansteuerschaltung für kapazitive Druckwandler
US5424650A (en) Capacitive pressure sensor having circuitry for eliminating stray capacitance
US4233848A (en) Strain gauge pressure transducer apparatus having an improved impedance bridge
US4584885A (en) Capacitive detector for transducers
US4586108A (en) Circuit for capacitive sensor made of brittle material
EP0944817B1 (de) Verfahren und vorrichtung zum elektronischen ausgleich von resonanz-messfehlern in einem kapazitiven druckwandler
US3318153A (en) Diode loop capacitor comparative circuit including a pair of transformer windings coupled in phase
JPS63259424A (ja) 圧電変換器の振動特性を測定する方法とその装置および圧電変換器の駆動方法
JP2652949B2 (ja) 圧力測定変換器
US4449409A (en) Pressure measurement system with a constant settlement time
US3967490A (en) Vibration densitometer
EP0238746B1 (de) Gasdruckwandler
JPH04504620A (ja) 圧電差圧渦センサー
US3657630A (en) Electro servosystem for a force balancing gauge
EP0560970A1 (de) Wirbeldurchflussmesser mit rauschunterdrückung
US3522528A (en) Noncontacting capacitance distance gauge having a servosystem and a position sensor
Hermann et al. Capacitive silicon differential pressure sensor
RU2808718C1 (ru) Пьезоэлектрический манометр для статических измерений
SU905671A1 (ru) Датчик давлени
SU1717947A1 (ru) Тензометрическое устройство
US3434340A (en) Method and apparatus for observing mechanical oscillations
JP3038497B2 (ja) 圧電差圧渦センサー
Pierre et al. A battery operated microsystem for flow measurements
RU8470U1 (ru) Емкостный уровнемер

Legal Events

Date Code Title Description
AS Assignment

Owner name: BALZERS AND LEYBOLD INSTRUMENTATION AB, FINLAND

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:OLSSON, RAY;BJORKMAN, PER;REEL/FRAME:010129/0707

Effective date: 19990519

STCF Information on status: patent grant

Free format text: PATENTED CASE

FPAY Fee payment

Year of fee payment: 4

FPAY Fee payment

Year of fee payment: 8

FPAY Fee payment

Year of fee payment: 12